Archaius 原理

Archaius 原理

Archaius是什么？

Archaius提供了动态修改配置的值的功能，在修改配置后，不需要重启应用服务。其核心思想就是轮询配置源，每一次迭代，检测配置是否更改，有更改重新更新配置。

一个简单的例子：

1. 获取配置源

/**
 * Created by longfei on 17/1/19.
 */
public class DynamicConfigurationSource implements PolledConfigurationSource {
    @Override
    public PollResult poll(boolean initial,Object checkPoint) throws Exception {
        Map<String,Object> map = new HashMap<>();
        map.put("test",UUID.randomUUID().toString());
        return PollResult.createFull(map);
    }
}

2. 定义调度器

AbstractPollingScheduler scheduler = new FixedDelayPollingScheduler(2000,2000,false);

3. 定义动态配置

DynamicConfiguration configuration = new DynamicConfiguration(source,scheduler);

4.简单单元测试

    @org.testng.annotations.Test
    public void testArchaius() throws Exception {
        PolledConfigurationSource source = new DynamicConfigurationSource();
        AbstractPollingScheduler scheduler = new FixedDelayPollingScheduler(2000,2000,false);
        DynamicConfiguration configuration = new DynamicConfiguration(source,scheduler);
        ConfigurationManager.install(configuration);
        final DynamicStringProperty stringProperty = DynamicPropertyFactory.getInstance().getStringProperty("test","nodata");
        Helpers.subscribePrint(Observable.interval(1,TimeUnit.SECONDS).take(20).doOnNext(new Action1<Long>() {
                    @Override
                    public void call(Long aLong) {
                        System.out.println(stringProperty.get());
                    }
                }),"test");
        TimeUnit.MINUTES.sleep(1);
    }

实现

1. 启动轮询任务

public synchronized void startPolling(PolledConfigurationSource source, AbstractPollingScheduler scheduler) {
    this.scheduler = scheduler;
    this.source = source;
    init(source, scheduler);
    scheduler.startPolling(source, this);        
}

2.轮询的Runnable和初始化：实现是一致的

    PollResult result = null;
    try {
       result = source.poll(false,getNextCheckPoint(checkPoint));
       checkPoint = result.getCheckPoint();
       fireEvent(EventType.POLL_SUCCESS, result, null);
       } catch (Throwable e) {
       log.error("Error getting result from polling source", e);
       fireEvent(EventType.POLL_FAILURE, null, e);
       return;
       }
       try {
          populateProperties(result, config);
       } catch (Throwable e) {
           log.error("Error occured applying properties", e);
      }                 

注意到，会调用source.poll方法，即PolledConfigurationSource的polled，我们实现的数据源接口，可以自定义数据源（jdbc,文件，scm等）